bio exam 2

3 types of selection (can refer to both natural and sexual selection)

directional, stabilizing, disruptive

directional selection

• Individuals at one phenotypic extreme have a higher fitness

• Ex: antibiotic resistance

• Phenotypic variation stays the same or decreases

stabilizing selection

• Individuals with an intermediate phenotype have higher fitness

• Selection against both extremes so there isn't actually anything making the middle higher but because both extremes are being selected against, the middle is most beneficial

• Phenotypic variation decreases

disruptive selection

• At both phenotypic extremes have a higher fitness

• Selection against the middle

• Phenotypic variation increases

Natural Selection Misconception 1: natural selection changes individuals (correct and explain)

• Corrected: evolution is change in allele frequencies in a population over time

  • Changes in individuals across their lifespan is not evolution

  • Learning is not a type of evolution (ex: a bear learning how to catch fish - the bear learned but did not evolve)

    • Selection for increased degrees of learning

Natural Selection Misconception 2: natural selection is goal oriented

• Corrected: natural selection occurs by acting upon advantageous mutations and existing variation

  • Mutations occur by chance, not on purpose: organisms cannot “will” a trait, evolution and natural selection can only act on existing variation

• Selection is not progressive (moving toward a goal of becoming an improved organism)

  • Different environments are different times will exert different evolutionary pressures

Natural Selection Misconception 3: natural selection leads to perfection

• Corrected: traits evolve from previously evolved traits, which can lead to vestigial traits

  • Vestigial traits are traits that have lost their original function

  • Have a legacy in ancestry but are not being used in the organism today

    • Ex: tailbone

• There are fitness trade-offs, where two traits that cannot be optimized simultaneously

  • Genetic constraints

Natural Selection Misconception 4: natural selection is the only process of evolution

• Corrected: natural selection in adaptive evolution but not the only process that changes populations

  • Genetic drift

  • Mutations

  • Gene flow

Sexual selection is selection caused factors related to _______

mating

Mating varies bc of _________

phenotype

Phenotype leads to higher or lower ________

fitness

Sexual selection is ________ (random / non random)

non random

Natural selection can impact __________ success

reproductive

Sexual selection is driven by __________________

the fundamental asymmetry of sex

Fundamental asymmetry of sex results in…

• Females are limited in their ability to…

• Males are limited in…

different selection pressures in males and females

• produce and provision eggs

  • Selection for traits in females that allow for increased egg production

• their access to female mates

  • Selection for traits in males that allows for access to more mating opportunities

Sex reversed mating systems

• When males will put more energy in

• Sexual selection acts on the female

  • Ex: Seahorses

Intersexual selection:

selection of an indivual of one sex for mating by an indivual of the other sex

• (female) Mate choice drives intersexual selection and can lead to very showy traits to attract a mate

• The ornamental trait occurs in the sex that displays to attract the mate

• Causes sexual dimorphism

  • Showy trait example: peacock wings, colorful etc.

sexual dimorphism:

where traits differ between the sexes of a species

Mate choice in intersexual selection is based on ___________

honest signals

“Honest signals”:

organisms select mate with traits that signal health and quality

• a showy trait is not always an honest signal, researchers have to test whether it is or isnt

• Females choose mates based on their showy traits

• Honest signals come with a cost (ex: make it harder to fly)

Intrasexual selection:

selection through competition for mates within one sex selects for traits that improve competitive ability

Sexual selection and natural selection can conflict such that traits preferred in mating can survival

decrease

Species:

group of organisms that exchange genes within the group but cannot do so with other groups

• Full reproductive isolation means different species

• Grizzly bears are one species, black bears are another species

Species can be defined using different concepts, what are the 3?

biological, morphological, phylogenetic

1: biological species concept:

Species are defined by having complete reproductive isolation such that individuals of two different species: Do not interbreed Or do not produce viable and fertile offspring when mating take place

• Species are defined by reproductive isolation

• Advantage:

  • directly links the process of speciation to defining and identifying species

• Disadvantages:

  • cannot be evaluated in fossils or species that reproduce asexually

  • Difficult to apply if populations don't overlap

  • Reproductive isolation can be a gradient

    • Hybrid: an individual whose parents are from different species

    • Ex: lions and tigers

difference between interbreeding and inbreeding

inbreeding: mating in the same species,

interbreeding: mating among different species

2: morphological species concept:

• Identify evolutionarily distinct lineages by differences in size, shape, or other morphological features

  • Indirect measure of difference

  • PCA (data processing)

  • Advantages:

    • Widely applicable and can apply to sexual, asexual, and fossil species

  • Disadvantages:

    • Polymorphic species with differing phenotypes may be named as two species

    • Cannot identify cryptic species; vary in traits other than morphology

  • Some bird species are indistinguishable by appearance

  • Picking distinguishing features can be subjective

3: Phylogenetic species concept:

• Identifies species based on evolutionary history where species are monophyletic groups

• Takes genetic data or trait data and builds phylogenetic tree that shows speciation

  • Advantages:

    • Widely applicable and can apply to sexual, asexual, and fossil species (typically the number 1 way for asexual)

    • Directly measures genetic trait or trait differentiation (more direct than other concepts)

  • Disadvantages:

    • Carefully estimated phylogenies are only available for a small subset of species

    • Leads to recognition of more species than other species concepts

Ex question:

Bird guides once listed the myrtle warbler and Audubon's warbler as distinct species. Recently, these birds have been classified as eastern and western forms of a single species, the yellow-rumped warbler. Which of the following pieces of evidence, if TRUE, would be the cause for this reclassification?

A. The two forms interbreed often in nature, producing viable hybrids

B. The two forms live in similar habitats

C. The two forms are very similar in coloration

D. The two forms have many genes in common

A

Prezygotic mechanisms: prevent mating among members of different species or the formation of a zygote following interspecies mating

• types of reproductive prezygotic isolation:

Temporal, habitat, behavioral

Temporal isolation:

Populations are isolated because they breed at different times

Habitat isolation:

Populations are isolated because they breed in different habitats

• Can happen when species use their habitat differently as well

Behavioral isolation:

populations do not interbreed because they have different courtship displays

2 types where mating occurs but a zygote is not produced:

mechanical, gametic barrier

Mechanical:

Mating fails because male and female reproductive structures are incompatible

Gametic barrier:

mating fails because eggs and sperm are incompatible

Postzygotic mechanism: results in failure of a fertilized zygote to survive, or survival of but sterility of the individual produced

• 2 types of postzygotic reproductive isolation

hybrid inviability, hybrid sterility

Hybrid inviability:

hybrid offspring do not develop normally and die at some point during early development

Hybrid sterility:

Hybrid offspring mature but are sterile as adults (can't produce their own offspring)

Ex question: Two populations of birds with different coloration live on opposite sides of a peninsula. The habitat between the populations is not suitable for these birds. When birds from the two populations are brought together, they produce young whose appearance is intermediate between the two parents. These offspring will breed with each other or with birds from either parent population, and all offspring of these pairings appear intermediate to various degrees.

What keeps the two populations separate?

• A. Temporal reproductive isolation

• B. Postzygotic reproductive isolation

• C. Hybrid inviability

• D. Habitat isolation

• E. Behavioral isolation

The two populations are ___________

• A. Different species under the morphological species concept but the same species under the biological species concept

• B. The same species under the morphological species concept

• C. Different species, under the phylogenetic concept

• D. The same species under the phylogenetic concept

• E. None of the above

D, A

Speciation:

Formation of a new species

• Starts with a population of a single ancestral species, ends in 2 different species

Speciation occurs when _________ is reduced between two populations

gene flow

• Gene flow makes populations more similar because of shared genetic material

• Gene flow stops speciation

Reduced gene flow drives speciation because it allows for _____________

genetic divergence

Ex question: A small number of birds arrive on an island from a neighboring larger island. This small population begins to adapt to the new food plants available on the island as selection favors those birds with larger beaks. About twice a year, one or two more birds from the neighboring island arrive. These new arrivals ________.

A. Speed up the process of speciation

B. Promote adaptation to the new food plants

C. Slow adaptation to the new food plants

D. Increase genetic differentiation between the birds on the two islands

C

geographic isolation

chance event physically separates population into subgroups

genetic isolation

the two populations are genetically isolated from one another due to the absense of gene flow

genetic divergence

The populations diverge due to mutation, genetic drift, and selection

allopatric speciation

genographic isolation of populations generates new species (most common type of speciation)

• A geographic barrier results in genetic differentiation

Dispersal:

movement of individuals from one place to another

Genetic divergence through dispersal is likely to be faster when the new population is ______ and geographically _____ the original population.

A. Small; close to

B. Small; far from

C. Large; close to

D. Large; far from

B

Founders’ effect can play a large role in __________ via _________

allopatric speciation; dispersal

Vicariance:

physical splitting of the habitat

• Slow formation of a barrier and speciation is occurring alongside the formation of the barrier

Sympatric speciation:

speciation occurs between populations in the same geographic area (very uncommon)

• Genetic differentiation occurs without a geographic barrier

___________ causes gene flow

polyploidy

Macroevolution:

describes patterns of speciation that shape global biodiversity

Phylogeny:

branching evolutionary history of related species

Phylogenetic trees:

allow us to visualize phylogeny

(parts of a phylogenetic tree): branch

a line representing a species through time, evolution occurs along the branches (every single line)

(parts of a phylogenetic tree): root

the most ancestral branch in the tree

(parts of a phylogenetic tree): tip

endpoint of the branch, usually represents a species but can show other taxonomic units

(parts of a phylogenetic tree): node

A point within the tree where the branch splits into two branches

• Shows divergence

• Tells us where the most recent common ancestor at the tips of the species fall

(parts of a phylogenetic tree): sister taxa

two taxa that split from a node, most closely related to each other

A ______ node means more closely related

newer

Outgroup:

a taxon that diverged before the taxa that are the focus of the study

monophyletic group

“one snip”

Paraphyletic:

an ancestral taxa and some but not all its descendants

Polyphyletic:

shares similar traits but does not include the common ancestor (because it does not have those traits)

Derived trait:

a character that is a modified form of the ancestral trait, found in a descendant

Synapomorphy:

A trait found in two or more taxa that is present in their most recent common ancestor but is missing in a more distant ancestor

• A trait that defines a monophyletic group

• The trait evolved right before the node that snips the monophyletic group

Synapomorphies are often more specific types of ___________

homologies

Homology:

when two organisms share a trait, this similarity is due to common ancestry

Homoplasy:

when similar traits evolved independently in two or more lineages and thus are similar for reasons other than lineage

Homoplasy evolves via ___________

convergent evolution

Convergent evolution:

independent evolution of similar traits in different species due to adaption to similar environmental conditions and a similar way of life

Parsimony:

the most likely explanation is the one that requires the fewest steps

Which of the following statements best describes the rationale for applying the principle of parsimony in constructing phylogenetic trees?

A. Parsimony allows the researcher to "root" the tree.

B. Homologous traits should be more common than homoplastic traits within a lineage

C. The molecular clock, which dates events on a phylogeny, validates the principle of parsimony.

D. The outgroup roots the tree, allowing the principle of parsimony to be applied.

B

Ecology:

the study of how organisms interact with each other and their environment

ecological scale

organisms, populations, communities, ecosystems, the biosphere

Organismal ecology:

study of how morphological, physiological, and behavioral adaptations increase fitness in a particular environment

Population ecology:

how the number and distribution of individuals in a population change over time

community (ecology):

Community: consists of population of different species that interact with each other within a particular area

Community ecology: ask questions about the nature and consequences of species interactions

ecosystem (ecology):

Ecosystem: consists of all the organisms in a particular region along with nonliving component

• Abiotic: nonliving components

• Biotic: living components

Ecosystem ecology: study how nutrients and energy move among organisms and through the surrounding atmosphere, soil, or water

biosphere (ecology):

Biosphere: a thin zone surrounding the earth where all life exists

• 5km below the land surface to over 10km up into the atmosphere

Global ecology: study the effects of human impacts on the biosphere

An ecologist decides to study the effect of how a fungal pathogen of bumblebees changes the reproductive success of bog sage, a plant species pollinated by the bumblebees. This is an example of a study at the ____________________ scale.

A. Organismal ecology

B. Population ecology

C. Community ecology

D. Ecosystem ecology

E. Global ecology

C

Global climate system is powered by ________

solar radiation

steps of solar radiation

1: high energy solar radiation comes to earth from the sun

2: 30% of the incoming radiation is reflected back into space

3: the other 70% is absorbed by the earth's surface and atmosphere

4: the earth radiates the absorbed radiation that back as lower energy radiation

5: greenhouse gases trap some of the outgoing longwave radiation

Greenhouse gases:

molecules with at least three atoms that can absorb and remit solar radiation (know water and carbon dioxide)

• Make up less than one percent of the atmosphere

• 78% nitrogen (N2)

• 21% oxygen (O2)

If the concentration of greenhouse gasses increased in the atmosphere, then

A. The amount of shortwave solar radiation reaching Earth would increase

B. The amount of shortwave solar radiation reaching Earth would decrease

C. The amount of longwave radiation escaping back into space would increase

D. The amount of longwave radiation escaping back into space would decrease

E. Temperatures would decrease

D

Temperature varies across the globe due to…

the shape of the earth

Hot air is ____ dense:

• Has _____ (higher/lower) pressure

• ______ (rises/falls)

• Holds _____ (more/less) water

less

• lower

• rises

• more

Cold air is ______ dense

• Has _______ (higher/lower) pressure

• _______ (rises/falls)

• Holds _____ (more/less) water

more

• higher

• falls

• less

Hadley cell results in…

heavy rainfall at the equator and deserts at 30 degrees latitude

There are 3 main cells that influence global patterns of precipitation:

1: hadley cell

2: mid latitudinal (ferrel) cell

3: polar cell

The direction and size of cells are determined by _________

tradewinds

The earth's ______ and ______ produces seasons

tilt and orbit

Seasonality:

degree of difference between summer and winter temperatures in a region (annual variation in temperature)

Seasonality increases with ________

latitude

As you move up in elevation, it gets _______

colder

rainshadow

a dry patch of land on the side of a mountain facing away from the prevailing wind, known as the leeward side.

explain the graph

This graph compares annual temperature cycles across three climate types. Equatorial climates stay warm and stable year-round (about 25°C), while continental temperate climates swing dramatically, from around −3°C in January to about 23°C in July. Maritime temperate climates fall in between, with milder seasonal change (roughly 7°C to 16°C) because nearby oceans moderate temperature extremes.